Currently, the infrastructure making up Ethernet Local Area Networks (LANs) and Wide Area Networks (WANs) is constructed to carry and distribute high bit rate data communication signals between network devices. The network devices or elements, may include, for example, hubs, switches, bridges, routers, interconnection equipment, various devices that are equipped with Network Interface Cards (NICs), data servers, desktop PCs, portable PCs and other various network equipment. What all these devices have in common, among other things, is that they all require electrical power in order to operate. In each case, the electrical power consumed by these devices is supplied by internal or external batteries or by AC power supplied from a power utility.
Today, every network element device that is not self energized, i.e., includes an internal or external battery, requires a connection to a source of electrical power in addition to one or more network connections. The requirement of network devices to connect to a source of electrical power complicates installation and makes it more costly. In addition, it limits the location of network elements to locations where electrical power connections and data network connections are available. Ultimately, two separate networks must be built and maintained, wherein each network is connected to the network device. One network supplies electrical power distribution and the other network supplies connectivity to the data communications network.
Further, for network devices to operate during partial or complete electrical power supply interruption or failure, each network device must either incorporate an internal battery backup system or must be connected to an Uninterruptable Power Supply (UPS). Depending on the application, such as with IP or LAN telephones, the number of network devices that must operate during building power failures may be very high.
Thus, it would be desirable to eliminate the need for each network device that does not operate from a battery to be connected to a source of AC utility power, i.e., a standard AC electrical receptacle, in addition to a network connection. This would significantly reduce the number of electrical cables, AC receptacles and associated connections thereby simplifying the installation of network devices. In addition, this would also provide a cost effective means for providing an uninterruptable power source to multiple network devices.
It is important to point out that the data communications network infrastructure was primarily designed and optimized to carry high bandwidth low power data communications signals and was not designed to deliver electrical power. The IEEE 802.3 standard requires that the electrical voltages carried over the transmitting cable be isolated and balanced in reference to earth ground at both ends. Category 3 to 5 LAN cables, RJ45 connectors, the line interface of network devices and all IEEE 802.3 compatible devices within the network were not designed to carry electrical power at a sufficient level to operate the majority of network devices.
Therefore, any solution that uses the LAN infrastructure to simultaneously distribute electrical power and provide network data communications should address the following points: (1) electrical power distribution over the LAN infrastructure should neither increase the network bit error rate (BER) beyond permissible levels nor disturb normal data communications in any way; (2) electrical power on the LAN infrastructure should not introduce any possibility of harm or risk to users and network maintenance personnel; (3) electrical power over the LAN infrastructure should not harm or cause damage to standard LAN equipment which is not designed to receive power from the data communications network; and (4) the addition of electrical power over the data communications network should not degrade the reliability of the network.
Systems for delivering data communication signals over power networks are known in the art. Power line carrier systems are well known and function to superimpose relatively high frequency data signals over low frequency power cabling. These systems, however, are designed to operate over power lines that are very different from the LAN. The LAN medium is designed and constructed to carry data communication signals. Thus, the cables, connectors, line interface circuitry and terminal devices are not designed to handle high levels of electrical power. This is very different from superimposing low energy level data communication signals over power line networks.
A block diagram illustrating an example prior art data communications network wherein network devices are coupled to the AC main utility power is shown in FIG. 1. This example network is presented to illustrate the various network elements that are typically found in a LAN environment. The network, generally referenced 10, comprises a combination WAN and/or LAN backbone 12 coupled to an IP telephony server 14 and/or to one or more other service providers 15 and also to a LAN bridge/router 16 which is connected to a source of AC power via electrical plug 22. The IP telephony server 14 functions to provide telephone service for a plurality of Internet or IP telephones 52, 36, 28.
The LAN bridge/router 16 is coupled to two LAN hubs or switches 18, 20. IP telephones 28, 36, laptop or other portable computer 32 and desktop computer 40 are coupled to LAN hub/switch 18 via network data connections 31. LAN hub/switch 18 is connected to a separate source of AC power via electrical plug 24. IP telephone 28, 36, portable computer 32 and desktop computer 40 are connected to a source of AC power via electrical plugs 30, 38, 34, 42, respectively.
The LAN hub/switch 20 is also coupled to a separate source of AC power via electrical plug 26. A video camera 44 (e.g., standard video camera or Web camera), portable computer 48 and IP telephone 52 are coupled to LAN hub/switch 20 via network data only connections 47. Video camera 44, portable computer 48 and IP telephone 52 are connected to a source of AC power via electrical plugs 46, 50, 54, respectively.
It is noted that each network device requires a separate data communications connection and a connection to a source of electrical power. The data networking connection is made in the normal manner using standard LAN cabling to conventional hubs, switches, routers, etc. Electrical power to each network device is supplied via a plurality of AC mains receptacles. Thus, each network device must be provided with at least two utility hook ups: one to the data communications network and the second to the AC electrical power network.